The society of Automotive Engineers donated a set of gear-car kits to the department. It is part of an intensive engineering program that could take several weeks to finish. I am trying to set them up to be a single lesson on gear ratios, to fit within this course. I also brought in a bicycle to allow students to feel the force-distance tradeoff for gears. Interestingly, the ratio of input sprockets (connected to the pedal) to output sprockets (connected to the back wheel) does NOT give the mechanical advantage, but its inverse. That's because when the number of sprockets decreases on the back wheel, the number of rotations of the wheel goes up! That forces them to reverse the normal input/output ratio we used for the other machines; my honors students found this tricky.
